26. 1875=3a^4

32. 10.56=12.4(1-r)^20

i don't understand this two problems. the two problems are color colded.
i hope it is ok to post this two problems in this thread. if not, sorry.

2. Originally Posted by comet2000
26. 1875=3a^4

32. 10.56=12.4(1-r)^20

i don't understand this two problems. the two problems are color colded.
i hope it is ok to post this two problems in this thread. if not, sorry.
1.
$\displaystyle 1875 = 3a^4$
Divide both sides by 3:
$\displaystyle 625 = a^4$
Do forth root on both sides:
$\displaystyle \sqrt[4] {625} = \sqrt[4] {a^4}$
$\displaystyle 5 = a$

2.
$\displaystyle 10.56 = 12.4(1-r)^{20}$
Divide both sides by 12.4:
$\displaystyle 0.8516... = (1-r)^{20}$
Do twenty root on both sides:
$\displaystyle \sqrt[20] {0.8516...} = \sqrt[20] {(1-r)^{20}}$
$\displaystyle 0.992... = 1-r$
$\displaystyle 0.992... + r= 1$
$\displaystyle r \approx 0.007999$